ProjectSummary/Abstract NeuronalCa2+signalingthroughendoplasmicreticulum(ER) localizedinositoltrisphosphate(IP3R)and ryanodinereceptors(RyR)mustbetightlyregulatedtomaintaincellviability,bothacutelyandoverthe lifetimeofanorganism.ExaggeratedERCa2+release(upto4 fold)hasbeenassociatedwithAlzheimerdisease (AD)mutationsexpressedincellculturesandyoungmice,butlittleisknownofCa2+dysregulationsduring thenormalandpathologicalagingprocessesusingadultandagedmodels.Thehypothesisisthatearly intracellularCa2+dysregulationrepresentsauniquecalcium opathythatcontributestolaterprogressionof AD,andisnotanaccleratedcomponentofnormalaging.AimIofthisstudywilldetermineanddifferentiate thedistinctrolesofneuronalIP3andRyCa2+channelsinanon transgeniccontrolmouseandthe3xTg AD mousemodelofAD.AimIIwillanalyzetheeffectsofageandADmutationsonthemagnitudeofthe exaggeratedERCa2+signals,determinedownstreameffectsonelectrophsyiologicalmembranepropertiesand synapticactivity,andparsethecontributionsofPS1,APP,andtaumutationsbycomparing3xTg AD, APP/Tau,PS1KIandNonTgcontrolmice.AimIIIwillseektopharmacologicallyreversetheexaggeratedER Ca2+releaseinthe3xTg ADneuronsandmeasureeffectsonamyloidplaquedeposition.Likewise,amyloid plaqueswillbeclearedinolder3xTg ADmiceusingimmunotherapytechniques,andestablishifthereisa functionalrelationshipbetweentheearlyCa2+dysregulationandADhistopathology.Thesestudiescombine electrophysiologicalrecordinginbrainslices,2 photonCa2+imaging,andflashphotolysisofcagedcompounds fromcontrol(non transgenic),3xTg AD,APP/TauandPS1KImiceatyoung,adult,andoldages. ImmunohistochemicaltechniqueswillbeusedtomapandquantifychangesintheexpressionofIP3RandRyR subtypes,andextentofADhistopathology.Thesefindingswillelucidateintracellularsignalingchangesand downstreameffectsonneuronalphysiologythatoccurbothinnormalaging,andinneurodegenerative disorderssuchasAD. Narrative: The objective of this study is to determine the functional relationship between early changes in neuronal Ca2+ signaling, and later pathophysiology associated with aging and Alzheimer's disease (AD). The results of this study will have scientific and clinical relevance by differentiating between neuronal signaling changes associated with normal aging and those associated with AD pathogenesis. Benefits to public health include the prospect for earlier AD diagnosis and novel therapeutic intervention, long before the onset of cognitive decline and irreversible histopathology.